Aliphatic polyester is attracting attention as biodegradable plastic that can be easily degraded in nature or “green” plastic that can be synthesized from recyclable carbon resources such as sugar or vegetable oil. Currently, as aliphatic polyester, polyester having a lactic acid backbone, such as polylactic acid, is practically used.
As a technology for producing aliphatic polyester such as polylactic acid using a recombinant microorganism, for example, the technology disclosed in Patent Document 1 (WO 2006/126796) is known. Patent Document 1 discloses recombinant Escherichia coli prepared by introducing a gene encoding an enzyme that converts lactic acid to lactic-acid CoA and a gene encoding an enzyme that synthesizes polyhydroxyalkanoate using lactic-acid CoA as a substrate into host Escherichia coli. According to the technology disclosed in Patent Document 1, a Clostridium propionicum-derived pct gene is used as a gene encoding an enzyme that converts lactic acid to lactic-acid CoA. Furthermore, according to this technology, a Pseudomonas sp. 61-3 strain-derived phaC2 gene is used as a gene encoding an enzyme that synthesizes polyhydroxyalkanoate using lactic-acid CoA as a substrate.
However, Patent Document 1 has problems in that the productivity of aliphatic polyester such as polylactic acid cannot be said to be sufficient, and various examinations for improvement of the productivity are insufficient. For example, Patent Document 2 (WO 2008/062999) discloses an attempt to enhance the capacity of synthesizing a lactic acid homopolymer or a polylactic acid copolymer using lactic-acid CoA as a substrate through introduction of a specific mutation into a phaC1 gene from the Pseudomonas sp. 6-19 strain.
The above technology for producing aliphatic polyester such as polylactic acid using a recombinant microorganism involves accumulating aliphatic polyester within the microorganism. Hence, target aliphatic polyester is recovered by disrupting the microorganism.